The Butterfly Cluster is an open cluster of stars in the southern constellation of Scorpius. Its name derives from the vague resemblance of its shape to a butterfly; the Trumpler classification of II 3 r indicates it is rich in stars with a high concentration and a large range of brightness. It is positioned 3.5° to the northwest of Messier 7 near the tail of Scorpius. The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham, Jr. has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbor the Ptolemy Cluster. Credit for the discovery is given to Jean-Philippe Loys de Chéseaux in 1746. Charles Messier added it to his Messier Catalog. Estimates of the Butterfly Cluster's distance have varied over the years. Wu et al. found a distance estimate of 1,590 light-years, giving it a spatial dimension of some 12 light years. Modern measurements show its total visual brightness to be magnitude 4.2.
The cluster is estimated to be 94.2 million years old. Cluster members show a higher abundance of elements heavier than helium compared to the Sun. 120 stars, ranging down to visual magnitude 15.1, have been identified as most cluster members. Most of the bright stars in this cluster are hot, blue B-type stars but the brightest member is a K-type orange giant star, BM Scorpii, which contrasts with its blue neighbours in photographs. BM Scorpii, is classed as a semiregular variable star, its brightness varying from magnitude +5.5 to magnitude +7.0. There are eight candidate chemically peculiar stars; the cluster is located 24.59 ± 0.13 kly from the Galactic Center and is following an orbit through the Milky Way galaxy with a low eccentricity of 0.03 and an orbital period of 204.2 Myr. At present it is 23 ly below the galactic plane, it will cross the plane every 29.4 Myr. List of open clusters Messier object Messier 6, SEDS Messier pages The Butterfly Cluster on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
Guillaume Le Gentil
Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil de la Galaisière was a French astronomer who discovered several nebulae and was appointed to the Royal Academy of Sciences. He made unsuccessful attempts to observe the 1769 transits of Venus from India, he was born in Coutances and first intended to enter the church before turning to astronomy. He discovered what are now known as the Messier objects M32, M36 and M38, as well as the nebulosity in M8, he was the first to catalogue the dark nebula sometimes known as Le Gentil 3, he was part of the international collaborative project organized by Mikhail Lomonosov to measure the distance to the Sun, by observing the transit of Venus at different points on the earth. Edmond Halley had suggested the idea, but it required careful measurements from different places on earth, the project was launched with more than a hundred observers dispatched to different parts of the globe, for observing the transit coming up in 1761; the French expedition turned out to be unlucky, the most unfortunate was Guillaume Le Gentil, who set out for Pondicherry, a French possession in India.
He set out from Paris in March 1760, reached Isle de France in July. However, the Seven Years' War had broken out between France and Britain in the meantime, hindering further passage east, he managed to gain passage on a frigate, bound for India's Coromandel Coast, he sailed in March 1761 with the intention of observing the transit from Pondicherry. Though the transit was only a few months away, on 6 June, he was assured that they would make it in time; the ship was spent five weeks at sea. By the time it got close to Pondicherry, the captain learned that the British had occupied the city, so the frigate was obliged to return to Isle de France; when 6 June came the sky was clear, but the ship was still at sea, he could not take astronomical observations with the vessel rolling about. After having come this far, he thought he might as well await the next transit of Venus, which would come in another eight years After spending some time mapping the eastern coast of Madagascar, he decided to record the 1769 transit from Manila in the Philippines.
Encountering hostility from the Spanish authorities there, he headed back to Pondicherry, restored to France by peace treaty in 1763, where he arrived in March 1768. He waited patiently. At last, the day in question arrived, but although the mornings in the preceding month had all been lovely, on this day the sky became overcast, Le Gentil saw nothing; the misfortune drove him to the brink of insanity, but at last he recovered enough strength to return to France. The return trip was first delayed by dysentery, further when his ship was caught in a storm and dropped him off at Île Bourbon, where he had to wait until a Spanish ship took him home, he arrived in Paris in October 1771, having been away for eleven years, only to find that he had been declared dead and been replaced in the Royal Academy of Sciences. His wife had remarried, all his relatives had "enthusiastically plundered his estate". Due to shipwrecks and wartime attacks on ships, none of the letters he had sent to the Academy or to his relatives had reached their destinations.
Lengthy litigation and the intervention of the king were required before he recovered his seat in the academy and lived happily for another 21 years. During the time he spent in India, Le Gentil examined local astronomical traditions and wrote several notes on the topic, he reported that the duration of the lunar eclipse of 30 August 1765 was predicted by a Tamil astronomer, based on the computation of the size and extent of the earth-shadow, was found short by 41 seconds, whereas the charts of Tobias Mayer were long by 68 seconds. Le Gentil is the subject of a play by Canadian playwright Maureen Hunter. Transit of Venus was first produced at the Manitoba Theatre Centre in 1992, it was subsequently made into an opera of the same name with music by Victor Davies, presented by Manitoba Opera in 2007, Opera Carolina in 2010. A detailed account of Le Gentil's expedition was published in a series of four articles by Helen Sawyer Hogg Le Gentil's own account was published in Voyage dans les mers de l'Inde, fait par ordre du Roi, à l'occasion du passage de Vénus, sur le disque du Soleil, le 6 juin 1761 & le 3 du même mois 1769 par M. Le Gentil, de l'académie royale des sciences.
Imprimé par ordre de sa Majesté, two volumes, Paris 1779 and 1781. Works by or about Guillaume Le Gentil in libraries Voyage dans les mers de l'Inde. Tome 1 Tome 2
HD 35519 is a giant star in the direction of open cluster Messier 38. It was once treated as a cluster member. HR 1794 Image HD 35519
Walter Scott Houston
Walter Scott Houston was an American popularizer of amateur astronomy. He wrote the "Deep-Sky Wonders" column in Sky and Telescope magazine from 1946 to 1993. Houston was born in Tippecanoe, Wisconsin in 1912, he attended the University of Wisconsin. After graduating, he taught at universities and public schools in Wisconsin, Alabama, Kansas and Connecticut. During World War II he was an instructor at the Advanced Navigation School for Army-Air Force pilots at Selman Field in Louisiana. In 1960 he moved to Connecticut, he remained in this position until his retirement in 1974. As a boy, Houston learned to build microscopes and telescopes and developed an interest in amateur astronomy, he soon observed all 103 star clusters in the Messier catalog. While at the University of Wisconsin he began observing variable stars and in 1931 he joined the American Association of Variable Star Observers, he contributed more than 12,000 variable star observations to AAVSO. While living in Kansas in the 1950s, Houston undertook radio monitoring of meteor activity.
His group operated the first automated data collection system designed by amateurs for continuous, long-term collection of meteor event data. The same method forms the basis for most forward scatter automated detection systems used today, although other methods are available. In 1955, Houston recruited a few dozen people as satellite spotters for Operation Moonwatch. In 1958, his Moonwatch station in Manhattan, Kansas was the first to catch sight of Explorer I, the United States' first satellite. Houston was active in raising funds for the project, by giving talks about satellite watching and asking for contributions, he was so successful that the president of Kansas State University included Houston's team in his annual science research summary, the Physics Department donated equipment to the group. Houston is best known for the "Deep-Sky Wonders" column which he wrote for Sky & Telescope which popularized the observing of deep sky objects, his final column appeared in 1994, the year after his death.
He published a regional newsletter called The Great Plains Observer, circulated to several thousand amateur astronomers. In 1959, Houston perpetrated a celebrated April Fool's hoax when he included an article in the April edition of the Great Plains Observer that made the following claim: Just last week Dr. Arthur Hayall of the University of the Sierras reports that the moons of Mars are artificial satellites... They are space stations in the most elaborate sense of the word... though the race that flung them so magnificently into orbit may be dead and gone, they still orbit as the greatest monument to intelligent accomplishment yet known to mankind. Both Dr. Hayall and the University of the Sierras were fictitious; the hoax soon gained worldwide attention when it was taken by a Soviet scientist, Iosif Shklovsky, in an interview with Komsomol Pravda. Gerald Kuiper of the Yerkes Observatory was quoted as saying about Shklovsky, "He is much too brilliant to believe such nonsense." The main-belt asteroid 3031 Houston, discovered by Edward Bowell at Anderson Mesa Station in 1984, was named in his honor.
The Walter Scott Houston Award of the North East Region Astronomical League, was named after him. In 1974 he was the recipient of the Astronomical League Award at the National A. L. Meeting in East Lansing, Michigan where he was the main speaker. Deep-Sky Wonders, a collection of his columns from Sky & Telescope; the "Walter Scott Houston Award" of the North East Region Astronomical League
Messier 4 or M4 is a globular cluster in the constellation of Scorpius. It was discovered by Philippe Loys de Chéseaux in 1745 and catalogued by Charles Messier in 1764, it was the first globular cluster. M4 is conspicuous in the smallest of telescopes as a fuzzy ball of light, it appears about the same size as the Moon in the sky. It is one of the easiest globular clusters to find, being located only 1.3 degrees west of the bright star Antares, with both objects being visible in a wide-field telescope. Modestly sized telescopes will begin to resolve individual stars, of which the brightest in M4 are of apparent magnitude 10.8. M4 measures 75 light years across, it features a characteristic "bar" structure across its core, visible to moderate sized telescopes. The structure consists of 11th magnitude stars and is 2.5' long and was first noted by William Herschel in 1783. At least 43 variable stars have been observed within M4. M4 is 7,200 light years away, the same distance as NGC 6397, making these the two closest globular clusters to the Solar System.
It has an estimated age of 12.2 billion years. In astronomy, the abundance of elements other than hydrogen and helium is called the metallicity, it is denoted by the abundance ratio of iron to hydrogen as compared to the Sun. For this cluster, the measured abundance of iron is equal to: = − 1.07 ± 0.01 This value is the logarithm of the ratio of iron to hydrogen relative to the same ratio in the Sun. Thus the cluster has an abundance of iron equal to 8.5% of the iron abundance in the Sun. Based upon the abundance measurements, there is evidence that this cluster hosts two distinct stellar populations; each of the populations is a group of stars. Thus the cluster may have undergone at least two separate cycles of star formation; the space velocity components of this cluster are = km/s. It is following an orbit through the Milky Way that has a period of million years and an eccentricity of 0.80 ± 0.03. During periapsis it comes within kpc from the galactic core, while at apoapsis it travels out to a distance of kpc.
The orbital inclination is at an angle of 23° ± 6° from the galactic plane, carrying it as much as kpc above the disk. When passing through the disk, this cluster does so at distances of less than 5 kpc from the galactic nucleus; the cluster undergoes tidal shock during each passage, which can cause the repeated shedding of stars. Thus the cluster may have been much more massive in the past. Photographs taken with the Hubble Space Telescope in 1995 have revealed white dwarf stars in M4 that are among the oldest known stars in the Milky Way Galaxy at an age of 13 billion years. One such white dwarf has been found to be a binary star with a pulsar companion, PSR B1620-26 and a planet orbiting it with a mass of 2.5 times that of Jupiter. In 1987 a millisecond pulsar was discovered in M4 with a period of 3.0 milliseconds, or about ten times faster than the Crab Pulsar. CX-1 Is located in M4, it is known as a possible millisecond pulsar/neutron star binary. It orbits in 6.31 hours. M4, SEDS Messier pages M4, Galactic Globular Clusters Database page "Hubble Space Telescope Finds Stellar Graveyard".
Hubble News Desk. 1995-08-28. Retrieved 2006-05-24. Gray, Meghan. "M4 – Globular Cluster". Deep Sky Videos. Brady Haran. Messier 4 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process, it is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometers, or 109 times that of Earth, its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System. Three quarters of the Sun's mass consists of hydrogen; the Sun is a G-type main-sequence star based on its spectral class. As such, it is informally and not accurately referred to as a yellow dwarf, it formed 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System; the central mass became so hot and dense that it initiated nuclear fusion in its core. It is thought that all stars form by this process.
The Sun is middle-aged. It fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result; this energy, which can take between 10,000 and 170,000 years to escape from its core, is the source of the Sun's light and heat. In about 5 billion years, when hydrogen fusion in its core has diminished to the point at which the Sun is no longer in hydrostatic equilibrium, its core will undergo a marked increase in density and temperature while its outer layers expand to become a red giant, it is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, render Earth uninhabitable. After this, it will shed its outer layers and become a dense type of cooling star known as a white dwarf, no longer produce energy by fusion, but still glow and give off heat from its previous fusion; the enormous effect of the Sun on Earth has been recognized since prehistoric times, the Sun has been regarded by some cultures as a deity.
The synodic rotation of Earth and its orbit around the Sun are the basis of solar calendars, one of, the predominant calendar in use today. The English proper name Sun may be related to south. Cognates to English sun appear in other Germanic languages, including Old Frisian sunne, Old Saxon sunna, Middle Dutch sonne, modern Dutch zon, Old High German sunna, modern German Sonne, Old Norse sunna, Gothic sunnō. All Germanic terms for the Sun stem from Proto-Germanic *sunnōn; the Latin name for the Sun, Sol, is not used in everyday English. Sol is used by planetary astronomers to refer to the duration of a solar day on another planet, such as Mars; the related word solar is the usual adjectival term used for the Sun, in terms such as solar day, solar eclipse, Solar System. A mean Earth solar day is 24 hours, whereas a mean Martian'sol' is 24 hours, 39 minutes, 35.244 seconds. The English weekday name Sunday stems from Old English and is a result of a Germanic interpretation of Latin dies solis, itself a translation of the Greek ἡμέρα ἡλίου.
The Sun is a G-type main-sequence star. The Sun has an absolute magnitude of +4.83, estimated to be brighter than about 85% of the stars in the Milky Way, most of which are red dwarfs. The Sun is heavy-element-rich, star; the formation of the Sun may have been triggered by shockwaves from more nearby supernovae. This is suggested by a high abundance of heavy elements in the Solar System, such as gold and uranium, relative to the abundances of these elements in so-called Population II, heavy-element-poor, stars; the heavy elements could most plausibly have been produced by endothermic nuclear reactions during a supernova, or by transmutation through neutron absorption within a massive second-generation star. The Sun is by far the brightest object in the Earth's sky, with an apparent magnitude of −26.74. This is about 13 billion times brighter than the next brightest star, which has an apparent magnitude of −1.46. The mean distance of the Sun's center to Earth's center is 1 astronomical unit, though the distance varies as Earth moves from perihelion in January to aphelion in July.
At this average distance, light travels from the Sun's horizon to Earth's horizon in about 8 minutes and 19 seconds, while light from the closest points of the Sun and Earth takes about two seconds less. The energy of this sunlight supports all life on Earth by photosynthesis, drives Earth's climate and weather; the Sun does not have a definite boundary, but its density decreases exponentially with increasing height above the photosphere. For the purpose of measurement, the Sun's radius is considered to be the distance from its center to the edge of the photosphere, the apparent visible surface of the Sun. By this measure, the Sun is a near-perfect sphere with an oblateness estimated at about 9 millionths, which means that its polar diameter differs from its equatorial diameter by only 10 kilometres; the tidal effect of the planets is weak and does not affect the shape of the Sun. The Sun rotates faster at its equator than at its poles; this differential rotation is caused by convective motion
Messier 7 or M7 designated NGC 6475 and sometimes known as the Ptolemy Cluster, is an open cluster of stars in the constellation of Scorpius. The cluster is detectable with the naked eye, close to the "stinger" of Scorpius. With a declination of -34.8°, it is the southernmost Messier object. M7 has been known since antiquity. Italian astronomer Giovanni Batista Hodierna counted 30 stars in it. In 1764, French astronomer Charles Messier catalogued the cluster as the seventh member in his list of comet-like objects. English astronomer John Herschel described it as "coarsely scattered clusters of stars". Telescopic observations of the cluster reveal about 80 stars within a field of view of 1.3° across. At the cluster's estimated distance of 980 light years this corresponds to an actual diameter of 25 light years; the tidal radius of the cluster is 40.1 ly and it has a combined mass of about 735 times the mass of the Sun. The age of the cluster is around 200 million years while the brightest member star is of magnitude 5.6.
In terms of composition, the cluster contains a similar abundance of elements other than hydrogen and helium as the Sun. On Aug. 29, 2006, Messier 7 was used for first light image of the Long Range Reconnaissance Imager telescope on the Pluto-bound New Horizons spacecraft. List of Messier objects List of open clusters New General Catalogue Messier 7, SEDS Messier pages Messier 7 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Sky Map and images NASA Astronomy Picture of the Day: M7: Open Star Cluster in Scorpius New Horizons probe captures M7 NASA Astronomy Picture of the Day: M7: Open Star Cluster in Scorpius